Roth Conversion Calculator

The converted amount is added to your ordinary income for the year, so the starting point is your federal bracket: 10% to 37% in 2026. The real cost is often higher, because the same income can make more Social Security taxable, push qualified dividends out of the 0% rate, shrink the senior deduction, trigger the 3.8% net investment income tax, cut an ACA premium credit and raise Medicare premiums two years later. The calculator adds all of these and divides by the amount converted.

Once your provisional income (other income plus half your benefits plus tax-exempt interest) passes $34,000 single or $44,000 joint, each extra dollar of income makes 85 cents more of your Social Security taxable. So one dollar of conversion adds up to $1.85 of taxable income: in the 12% bracket that is about 22%, and in the 22% bracket about 41%, until 85% of your benefits are taxable and the effect stops. These thresholds are not adjusted for inflation.

Yes, two years later. Medicare sets Part B and Part D surcharges (IRMAA) from your modified adjusted gross income two years earlier, so a 2026 conversion affects 2028 premiums. The surcharge rises in steps: in 2026, a single person with MAGI over $109,000 pays $81.20 a month more for Part B plus $14.50 for Part D, and the steps go up to $487 plus $91 a month at $500,000. One dollar over a line costs the whole year's step, for each person on Medicare.

From 2025 through 2028, each person aged 65 or older can deduct an extra $6,000, whether or not they itemize. Each $6,000 shrinks by 6% of modified AGI above $75,000 single or $150,000 joint, so a single filer loses it all at $175,000 and a couple who are both 65 or older at $250,000. A conversion that raises your income into that range costs you the deduction as well as the tax: about 6% of your bracket on each dollar for one senior, 12% for two.

Yes. The premium tax credit is based on household income, which includes the conversion. The more you convert, the more you are expected to pay toward the benchmark silver plan, and above 400% of the poverty line the credit stops entirely now that the enhanced credits of 2021–2025 have ended. For a household of two in the 48 states, 400% of the line for 2026 coverage is $84,600. Since 2026, any advance credit you received above what you qualify for must be paid back in full when you file.

If any of your traditional, SEP or SIMPLE IRAs hold after-tax (nondeductible) money, you cannot convert just that part. Form 8606 spreads the after-tax basis across all your IRA balances at 31 December plus the amount converted, and only that share of the conversion is tax-free. Money in a 401(k) is not counted.

There is no 10% penalty on the conversion itself, and no income limit. A conversion counts in the year the money leaves the IRA, so a 2026 conversion must be completed by 31 December 2026. Since 2018 a conversion cannot be undone. If you are under 59½, each converted amount has its own five-year clock before it can be withdrawn without the 10% penalty. From age 73, the year's required minimum distribution must be taken first and cannot itself be converted.

If the money grows the same either way, converting comes out ahead only when the rate you pay now is lower than the rate you, a surviving spouse or your heirs would pay on the withdrawal later. That later rate should count the same hidden costs, which is why the calculator shows a real rate rather than a bracket. Paying the tax from money outside the IRA tilts the result a little toward converting. The comparison depends on your future income, which only you can judge.